YOUNG DOBBS’ HAT.[A tragic story for Magic Lantern or Shadow Show.]
1. When Dobbs was a little boy, he was not so particular with his hats as he was when he grew up to young-manhood. For instance, on the very day he wore his first tall one he encountered a magnificent specimen of the cabbage butterfly.
1. When Dobbs was a little boy, he was not so particular with his hats as he was when he grew up to young-manhood. For instance, on the very day he wore his first tall one he encountered a magnificent specimen of the cabbage butterfly.
2. Now he much wanted a cabbage butterfly to complete his collection, so he made straight at it. In the pursuit his hat suffered.
2. Now he much wanted a cabbage butterfly to complete his collection, so he made straight at it. In the pursuit his hat suffered.
3. So did he when he got home! As for the butterfly, I have every reason to believe it died a natural death some time later.
3. So did he when he got home! As for the butterfly, I have every reason to believe it died a natural death some time later.
Every boy at some time or other, I suppose, has felt himself irresistibly drawn towards the subject of toy-balloons; but first unaided experiments in that direction seldom prove altogether satisfactory, or maybe even pleasant. It is my intention, therefore, to go into the matter thoroughly and practically, explaining all about fire-balloons, and telling you at once how to make and use them.
If a thing—anything—be placed in the midst of any other thing lighter than itself, and if thing number two be not a solid, but either a liquid or a gas, both which permit of motion in any direction, then thing number one will ascend.
If you want to have this demonstrated, just plunge a cork down into water and see what happens. If instead of a cork you were to take a lump of iron—say a cannon ball—then the very idea of such a heavy material floating would seem to you ridiculous. It will float, nevertheless, not in water, truly, but in any fluid of greater weight than itself. Quicksilver, otherwise called mercury, is such a fluid, and the very experiment I have supposed you to perform for curiosity is actually turned to practical account by artillerists when they wish to ascertain whether a cannon ball is equally heavy on every part of corresponding size around the centre. If not equally heavy, then spots marked upon it will not float upwards equally well. If any particular spot insists on turning downwards, then the result proves that one side of the round cannon ball (please excuse the word side, a sphere really has no sides) is heavier than the rest.
But to return to our balloons. Well, please remember the globe on which we live is surrounded by an atmosphere—air we call it—and also please understand this atmosphere has weight; consequently it follows that anything lighter than the atmosphere will ascend in the atmosphere. In this we have the whole theory of balloons and ballooning.
The air has weight,—yes, more than you have been accustomed to think, perhaps. Just take the pen or pencil and mark out a piece of paper one square inch. Having marked out this, you are to understand that the air presses upon it with a force of about fifteen pounds. I sayabout, for the reason that atmospheric pressure is not always exactly the same. Sometimes it presses rather more, at other times rather less than fifteen pounds, but still the variation is not great.
Thus, air has weight, and you also know that air, being a fluid, permits objects to move about in it, so it follows that if we can find anything number two lighter than the air, it will ascend in the air. We shall look in vain amongst liquids and solids for thing number two, all being heavier than air; but of gases lighter than air there exist several. Why not use them? We can use some of them, and we presentlywill; but it stands to reason that we can no more use a gas for lifting a weight up into air without first putting the gas into a bag, than we can use a horse for carriage-draught without first putting a collar round his neck, then attaching shaft and traces: no, indeed, not so well even, because in a case of emergency a carriage might be fixed to the horse’s tail!
The very simplest form of balloon is a soap-bubble. Most of us have probably at some time or other amused ourselves by blowing soap-bubbles, without perhaps troubling ourselves to understand the whys and wherefores of the case.
Why is it that a soap-bubble blown with air from the lungs ascends? You will tell me perhaps that it ascends because the air which comes from the lungs is of a lighter ‘nature’ than the atmosphere No, indeed, instead of having a lighter it has a heavier nature. Though air which comes out of the lungs is by ‘nature’heavierthan air which goes into the lungs, yet at the same time it is warmer, and for the reason of that warmth it remains during the existence of the warmth practically lighter.
This circumstance being remembered, you will at once understand why it is that a soap-bubble, even if it lives—so to put the case—long enough, does not continue to ascend as a balloon would have continued, but first slackens in its upward course, then descends, the reason of descent being the cooling of the air within it. If you had been clever enough to measure that soap-bubble twice, first at the very moment of rising, next at the last moment of setting, you would have found the warmer bubble to have been the larger.
If you were to blow a thin bag full of air, you would not expect it to ascend, on the supposition, that is to say, that the bagged air and the free air are of one and the same temperature; but if you could manage to make the bagged air hot, and keep it hot, then you would get lifting power. This is exactly what is done in the Montgolfier, or fire-balloon.
The reason of this seems very simple when one comes to think about it, yet the Brothers Montgolfier, inventors of the fire-balloon, did not exactly see the true science of the balloon that bears their name. They appeared to have reasoned somewhat in the following manner. A wreath of smoke ascends, therefore smoke must be lighter than air; therefore a bag filled with smoke, and kept full of smoke, should also ascend, supposing the bag to be made of sufficiently light materials.
If the Montgolfiers had said, instead of smoke, hot air, they would have truly represented the fact.
They made a bag of canvas, and they lined it with paper. Under the neck of this bag they hung a sort of fire-grate, and underneath this, but within reach of it, a car. Impressed as they were with the smoky notion, one of their first cares was to feed the fireplace with some variety of fuel that would yield abundant smoke. Chopped straw, slightly damped and mixed with wool, was one of the favoured combustibles.
Fire, or Montgolfier balloons, large enough to take up sky travellers, are no longer used; air-balloons, or, as it would be more proper to call them, gas-balloons, being more convenient and at the same time more safe. Toy fire-balloons are, however, still made and let off as a pretty firework, and I shall now describe the best and easiest ways of making them.
They may be constructed of any size; but an overgrown fire-balloon, according to my experience, is seldom satisfactory, and never returns value for the money expended in making it. As a boy I was a great fire-balloon maker. I have made them of various sizes; at length, however, coming to the conclusion that three sheets of tissue-paper, pasted end to end, then cut into shape and joined, make a balloon quite large enough to manage, and also large enough for every ornamental purpose.
‘Cut into shape,’ did I not say the paper was to be? Well, what sort of a shape? Perhaps I need not tell you that a perfectly globular bag will hold more than any other shaped bag you could make out of a given quantity of paper. A peeled orange or lemon will give the very best idea of the general shape of the gussets of a balloon. Speaking generally, the narrower you cut the gussets of your balloon the neater will be your turn out; but of course, if narrow gussets be employed, more of them will be needed than if you employed wide gussets. Neatness of manufacture is of no account when brought to bear on a toy firework that, after a few moments of ascent, reveals itself to lookers-on merely as a patch of moving light.
baloonFig. 1.balloonFig. 2.
baloonFig. 1.
Fig. 1.
balloonFig. 2.
Fig. 2.
After many trials, I came to the conclusion that when using tissue-paper, three sheets pasted narrow edge to narrow edge, eight gussets were enough. Occasionally, however, I would slightly elongate each gusset by attaching one of the little cornersaorb, and fixing it atc. Of course the piecesaandbhave to be cut away in any case, else the necessary gussets could not be made.
With regard to the exact shape of a finished balloon, always remember that the more nearly globular it is the more gas or air will it hold, and the more stable will be its flight. Assuming you to have pasted end to end three sheets of tissue-paper, with the little bit (c) added to the top part over and above, I recommend you to divide, mentally at least, the three sheets and bit added, rectangle, into four parts. Of these the two middle parts need not be cut or trimmed at all. All the trimming needful can be done on the two end parts. Another thing—do not give any care to bringing the crown, or summit, of the balloon to a point. You will have to paste on what we call a round summit, or crown, at any rate, under which circumstance your bringing all the gussets to one terminal point is of no consequence. In cutting out the gussets, this is best done on the double, which will ensure symmetry.
You will tell me, perhaps, there is a sort of regularity about my preliminary workthat does not please the eye. You would like, perhaps, to make a graceful balloon likeFig. 3.
Better not. Do you not see what would happen when you came to set light to the fuel suspended under the mouth of the balloon? The flame would almost certainly strike against the paper of the narrow neck, and presently the whole balloon would be in a blaze.
Having cut out your gussets, the next thing is to join them. First as to cement. Use thin paste or gum water, which you please, and employ a camel-hair, or better, a sable-brush, to spread it. Half an inch lap is quite enough; and when the necessary paper junction has been made, I like to dry my work at once by means of a laundress’s smoothing iron. Taking this precaution, you will have no sticking at spots where sticking ought not to be.
A final word now about the best way of bringing the edges of your gussets together. The line diagram here given will make all comprehensible:aandbrepresent, we will say, two gussets.
The edge ofais alone to be gummed or pasted to about half an inch wide; the corresponding edge ofbis then to be bent down upon the cemented edge ofa, and dried at once with the laundress’s hot iron; not laid naked upon the paper, but having a thickness of flannel interposed. Proceeding thus all round, you will at last finish your balloon all but the crown pieces and mouth stiffener. For a balloon of the dimensions recommended, I would advise you to paste on a crown piece of about a foot diameter. Don’t make it of tissue-paper, but of soft whitey brown paper, and in the middle of it paste a loop of calico, something similar to the loop of a saucepan lid. The utility of this will be found out when you come to let off your balloon.
As a mouth stiffener I prefer a circle of thick iron or brass wire to anything else. About three inches from the balloon-mouth had better be strengthened by a layer of calico, which being gashed or scalloped (Fig. 5), pasted and turned over the wire hoop, makes all firm. As to dimensions of mouth, I consider a circle of eighteen inches’ diameter quite big enough, and boys will please remember that three times and about one-seventh of a diameter makes the circumference of a circle.
Having made your balloon, the next thing to do, as it would seem, is to let it off.
Not exactly. You expect your balloon to lift a weight—fireworks probably—which I will describe how to manage by-and-by. It will be necessary, then, to learn by experiment how much weight it will carry; otherwise, when the time of letting off arrives, you may fail altogether, and be much disappointed.
The weight-carrying experiment must be performed in a room, to avoid air-currents, and, as a preliminary, some sort of car must be attached to the balloon for the purpose of holding the weights. The car may be of various shapes, but as good a shape as any is this:—
Fig. 7.—CAR.
Fig. 7.—CAR.
It may be made out of cardboard, or, if you like, of wire. You need not be particular about any sort of elegance. Fire-balloons are designed to be sent on their travels at night, when any sort of ornament or elegance lavished on the car would not be seen.
The usual flame for heating the air in a paper balloon is spirits of wine. Methylated spirit does very well, and is much cheaper than pure spirits of wine. I do not recommend this source of flame when the balloon comes to be actually let off, as you will by-and-by see; but for our present experiment I do recommend it. You must make a note of the weight of spirits of wine presently to be used, and, if you do not happen to have scales and weights handy, you may take it for granted that a sherry wineglass full weighs about an ounce.
Ascertain, too, how much the car weighs. Probably, when the time comes for letting off the balloon, you will not require the car, so you should have ascertained its weight, that you may supply a weight equivalent, in the shape of fireworks, for example.
Fig. 8.—CHAMBER TRIAL OF THE BALLOON.
Fig. 8.—CHAMBER TRIAL OF THE BALLOON.
Two boys will be wanted for performance of the chamber experiment; one to stand upon a chair or stool, so as to be able to lift the crown of the balloon, the other to manage the flame department—to do what engineers would call the stoking (Fig. 8).
The spirit, you will remember, is not to be burned loosely, but absorbed by something or other. Sponge is the absorptive medium usually employed, though some operators use cotton wick. On the present occasion of chamber experiment I recommend you to employ sponge. The very coarsest sponge will do as well as the finest and most expensive. Such a piece as most oilmen sell under the nameof ‘slate sponge,’ and generally for a penny, will do quite well for the chamber experiment.
Let me now give you boys a piece of advice, and do not consider it of small value. It is of enormous value, being the value of the difference between success and failure. I do not only mean success or failure in the experiment you are about to perform, but any experiment. The advice is this:—Attend well to detail. Before you set about performing any experiment take care that you have provided, and arranged well to hand, everything necessary to the performance of the experiment. Do not say to yourself, this, that, or the other is a trifle, and as a trifle neglect it. In all experimental work, having once determined in your own mind the various things and arrangements necessary, nothing amongst them can be a trifle. Well, to the point. Provide yourself, by loan if your pocket-money does not run so far, with some handfuls of farthings. This little coin will be about the most convenient thing you can use for seeing how much weight your balloon will take up. You are ready. Well, No. 1, as I will call you, lay hold of the crown of the balloon, then jump on a stool or chair, lifting the entire balloon up in such way that the mouth of it may be conveniently disposed for what has to be done by No. 2.
Previous arrangements having been made, it will be well, to avoid accidents, for No. 2 to partially inflate the balloon by a fan. Were this precaution not taken, it might happen that flame driven against the tissue-paper might set it on fire. Those who have not tried the experiment little know what power there is in a fan to set up and keep going a current of air. Sometimes people revive a sluggish fire by hanging a sheet of paper in front of it, but a far better application of the paper is to squeeze it into a rough fan and begin fanning. My attention was first called to this fire-fanning process when, travelling in Andalusia, I wanted some chocolate in a hurry, at a lonely waysideposada. A damsel, fan in hand, lighted a bit of charcoal with a paper spill, laid it on the stove grating, put other charcoal round it, the chocolate-pot over all, and began fanning.
You are now ready to learn how much weight your balloon will carry. You will have attached the car, of course. You will have laid your bit of sponge on the tin pan already attached, and you will have remembered to steady the sponge and keep it from falling out by passing a little iron binding wire over the surface of it, and attaching the wire to the tin pan. All this having been done, you are to pour the spirits of wine upon the sponge and set fire to it. Presently the balloon, becoming charged with hot air, will fill out and rise. When risen, be prepared with your money—farthings. Throw in farthing upon farthing until your balloon not only can carry no more, but comes down. Let it come down, and let the spirit flame burn quite out. Any attempt at blowing it out would probably set the balloon in a blaze.
You have gained now the information required; you have learned what weight, when the serious time of letting off arrives, your balloon will carry. Count the farthings and make a memorandum of their weight. There is no particular mystery in the choice of farthings; they are cheap enough, and they are small enough. Sovereigns and half-sovereigns will do quite well, and if you are sufficiently ‘warm’ in pocket-money, you may employ them instead of farthings, over which they present the advantage of recording the actual weight. A sovereign newly mintedweighs one hundred and twenty-three grains and a small fraction; a half-sovereign half that weight. Taking one sovereign with another, you may assume one hundred and twenty-three grains to be the weight of each. Here, by the way, I may mention that, having weighed hundreds of sovereigns for the sake of a lazy experiment, I never yet met with two of exactly the same weight.
Fig. 9.—LETTING OFF THE BALLOON.
Fig. 9.—LETTING OFF THE BALLOON.
A fire-balloon is a pretty device of itself, but it becomes much better worth looking at when it is made to take up fireworks, so I will now give some instructions about these fireworks. I cannot recommend you to make the fireworks yourselves, but to buy them ready made and arrange them in suitable devices. You will want a few feet of Bickford’s fuse, and the same of quickmatch. Both may be obtained of Messrs. Brock, of Cheapside and the Crystal Palace.
Fig. 10.—BICKFORD’S FUSE.balloonFig. 11.
Fig. 10.—BICKFORD’S FUSE.
Fig. 10.—BICKFORD’S FUSE.
balloonFig. 11.
Fig. 11.
Bickford’s fuse is much used by miners for exploding their charges. For this purpose it is invaluable, a given length burning a given time, so that the miner knows exactly what his fuse must be in order to afford him the time necessary for escaping to a safe distance before his charge goes off. It is invaluable to you boy balloonists in another way. The prettiest balloon firework effects are those which are not lighted at the time when you let off your balloon, but which take fire apparently of themselves after the balloon has gained a considerable elevation. Bickford’s fuse enables you to accomplish this in a manner you will soon understand.
Looked at casually, Bickford’s fuse might be taken for a piece of black cord, something in size like this (Fig. 10). The outside is of woven materialmade waterproof. The middle contains an inflammable wick, burning regularly to time.
If you were to pass through a length of Bickford’s fuse transversely a thread fixed at its upper end, and having a weight attached to the other end, and if then you were to light the fuse at one end, you see what would happen. The fire would creep along until, coming to the thread, it would burn the latter, and the weight would fall. It is many years since I had occasion to work with Bickford’s fuse, so I forget its rapidity of burning. It does not signify; when you have got your fuse you can try an experiment with any convenient length, timing the rapidity of burning by a watch.
Quickmatch consists of a paper tube with a rapidly inflammable wick running through it, the intention being that flame applied to one end of the match shall flash to the other, and instantaneously. The actual fireworks I recommend you to get are some blue-lights, some Roman candles, a few Catherine wheels, crackers, and maroons. The Roman candles you will only require to pick to pieces for the sake of the stars they contain, so if you could get the stars you would not want the candles. Mr. Brock, I think, would supply you with stars of various colours. He uses small pill-boxes for holding the star material.
I have now to explain to you a few fireworks for your balloon.
balloonFig. 12.
Fig. 12.
1.Fixed piece of blue-lights.—Having selected a cork of suitable size, bore its circumference with as many holes not going to the middle as you design to have blue-lights. Each excavation made will receive the blank end of a blue-light, just as a candlestick receives the end of a candle, so that when finished, supposing you to have used four blue-lights, you will have made something like this (Fig. 12).
balloonFig. 13.
Fig. 13.
On observing the blue-lights which you have purchased, each will be found to have attached to it at the burning end a screw of soft paper, usually blue. This I hardly need tell any English boy is touch-paper, made by saturating soft paper with solution of nitre and drying. Firework cases are usually finished off with touch-paper, so that they may ignite immediately. When you send up such an arrangement of blue-lights as just described, the proposition will be to ignite them all at once with a flash, and after the lapse of a period of time which must be left to your own discretion. Quickmatch spread from end to end of each blue-light, and there secured, either by thread or else a slip of paper pasted loopwise over it, will accomplish the first, and a suitable length of Bickford’s fuse the second. All this isobvious, but a diagram is given (Fig. 13). Hardly necessary is it to tell you that we want no car when using this device. A wire being passed through the middle of the cork hooked at one end, for attachment to hooked cross wires, and bent at the other end so that it shall not slip through the cork, are also obvious matters.
You will observe that I have represented the quickmatch as actually running through the Bickford transversely. This is the surest plan in this and all similar cases, because the walls of the Bickford are so thick that some time must elapse before they burn quite through. Transverse perforation and stretching out of the Bickford can easily be done, the walls of the fuse being very tough. Though my remarks have been directed to blue-lights only, yet obviously the arrangement applies to any other variety of tint.
balloonFig. 14.
Fig. 14.
2.Dropping firework devices.—Some of the prettiest balloon firework effects are those which do not light until they have separated from the balloon and fallen through a varying distance, according to your arrangement. I shall not expect to find that you think it necessary to inquire how all this may be managed after what I have written about Bickford fuse and quickmatch. However, some few remarks about a certain convenience of arrangement may not come amiss. Suppose, then, that you have launched your balloon carrying several devices—we will assume it to carry six. You want the first of these devices to part company with the balloon, and shortly after ignite in falling, all to time. You want the successive five to part company with the balloon also to time. Obviously a length of Bickford fuse will accomplish all this, but there are inconvenient as well as convenient ways of arranging all. A convenient way is this (Fig. 14).
When I have told you this diagram represents a thing made of wire, and you are so to use it that a fall shall take place at every corner, you will see that all can be managed by Bickford fuse.
Amongst the fireworks that are effective when thus falling are small blue-lights, squibs, crackers, maroons, stars, but more especially catherine wheels. All explosive fireworks give a shock when exploded—maroons a great shock. Never, then, use a balloon-attached firework in such manner as that it shall explode whilst attached to the balloon, the steadiness of which it would certainly affect—perhaps cause a tongue of flame to come in contact with the paper and set it on fire. A wirework arrangement such as our diagram represents is only intended to carry six successive devices, and for the devices that have been noted you will most likely find that about half-a-dozen will make up the total weight your balloon can carry. But there are certain lighter fireworks, of which considerably more than six may be carried; for example, stars. If you take a star and enclose it in a tissue-paper bag, together with a very little—say half a saltspoonful of mealed, or powdered, gunpowder; then, if you tie the mouth of the bag round a short length of quickmatch, you see what must happen when the flame of a Bickford fuse sets the free end of the quickmatch alight. You will rig up the stars with their bags on wire cross-work as already described, but you will arrange that the successive ignitions follow a spiral course, like that of a loosely-coiled watch spring.
I think I have told you as much as can be profitable about the making of fire-balloons, so a few words now about parachutes. People who ascend in the cars of large balloons sometimes vary the display by cutting connection with the balloonitself when at a certain height, and coming down by aid of a parachute. Parachutes used on these occasions are somewhat elaborate things, bearing a general resemblance to an umbrella deprived of its stick and ribs, having a cord attached to the spot where the terminal of each rib, if present, would have been, these cords all converging to join at their lower ends with a car.
balloonFig. 15.
Fig. 15.
The parachute I shall describe for your fire-balloons is a more simple affair, and is made as follows:—Provide yourself with two sheets of soft whitey-brown paper, some twine, and some paste. Lay one sheet flat on a table, and then extend diagonally from corner to corner two lengths of twine which must project at least six inches beyond each corner. It may be wanted to project even more, but in that case each cord terminal may be easily lengthened to the desired extent by tying the necessary additional length of twine to it. Now spread a film of thin paste evenly by a brush over the sheet of paper and twine, and then close the second sheet of paper in exact correspondence with the first, as represented in the diagram.
Be particular, in sticking the two sheets of paper together, to avoid formation of air bubbles. This can only be done by making the pasting together successive and not instantaneous—that is to say, do not lay the second sheet of paper flat down upon the first sheet all at once, but having begun to effect the attachment at any one edge, follow on deliberately to the opposite edge, patting the two sheets well together with a soft pocket-handkerchief.
The way of using such a parachute hardly needs explanation. The projecting lengths of twine having been brought together, are attached to a car, and the whole suspended to your balloon, from which you intend that it shall separate and begin to fall, on your balloon attaining the desired elevation. This detachment can easily be effected by Bickford’s fuse. Here, whilst I think of it, never attempt to ignite a Bickford fuse with anything else than the flame of a port-fire or a blue-light. The chief beauty of any firework device consists in working to exact time. A Bickford fuse cannot readily be set on fire with a match-flame. You may crack many lucifers over the job without succeeding; your balloon, that ought to be off on its travels, all the time kept waiting.
balloonFig. 16.
Fig. 16.
What will you put in the car? I shall leave this pretty much to your own taste. Some sort of weight there must be to pull the parachute down. I have heard of some boys who for ornament peopled the car with little figures of comical men, cut out of cardboard. I don’t see myself the sense of it. Fire-balloons are usually let off at night, when the little caricatures would almost need a spyglass to see them even before the balloon set out on its explorations. Balloons once off nobody could see the little men at all. However, do as you like, boys;hereare two notions of such caricature men.
Attention! The point up to which you and I have been working is near. We are going to let off the balloon. When we were making our chamber trial, you will remember we used methylated spirit for fuel, absorbing it by a sponge. You may use the same sort of fuel now if you please, but as for myself I much prefer the good flare of cotton lamp-wick saturated with tallow, and sprinkled with either benzoline or turpentine, so that it may burst into flame without delay at the first touch of other flame. Not only does tallow burn with a far brighter light than spirits of wine, but the flame is more lasting. However, boys, I say again—do as you like. So now farewell to fire-balloons. I will now proceed to tell you how to make and fill so-called air-balloons, though gas-balloons would be a name more fitting. They are not of themselves illuminative, as fire-balloons are, but they will take up any fireworks you please, according to their weight-carrying capabilities.
H
aving got fire-balloons out of hand, I will now have some words with you about air-balloons, usually so called, though ‘gas-balloons’ would be a more appropriate designation. Before describing how to make an air-balloon, suppose we gossip a little about the science of the thing.
Of gases there are many sorts, as you will become aware when a little advanced in your chemistry. Atmospheric air is a mixture of two gases, as probably you know—four measures of nitrogen to one of oxygen, roughly speaking; though were we describing the composition of atmospheric air in an exhaustive manner, we should have to chronicle the presence of numerous other gases besides oxygen and nitrogen, and some vapours; all, however, in quantities so extremely small that we need take no account of them here. Some gases are lighter than atmospheric air, some heavier, but it is evident that those only which are lighter can be employed for ballooning. The very lightest of all gases is hydrogen, which therefore is the very best gas for filling balloons. It is seldom now employed, however, coal-gas being usually substituted, on account of its being ready to hand, so to say, in every place where coal-gas illumination is practised.
Here, perhaps, some young gentleman will wish to inquire why it is I employ the ordinary name, coal-gas, instead of a chemical name. The reply is simple. Coal-gas always means gas from coal, but when I tell my readers that coal-gas has not necessarily always the same composition, although the same coal be used, they will see that no unchanging chemical name for it is applicable. According as the gas retort is heated more or less, so will the resulting gas differ in composition—not a difference as to nature of components, but as to quantity. Coal-gas must always be a combination of carbon with hydrogen, but the amount of carbon to a given amount of hydrogen may vary within wide limits. If coal-gas be required for illuminative purposes, the object of manufacture will be to make it as rich in carbon as possible. Now, the richest gaseous combination of carbon with hydrogen isolefiant gas, but it would be the worst quality of coal-gas for balloon inflation. If olefiant gas be transmitted through a white-hot iron pipe it expands in volume, thus showing what would have happened had it originally been produced in a white-hot iron retort. A gas manager doing duty in one of our seaport towns once told me that he always managed to have expanded gas—we may call it adulterated gas—for night street service. It was good enough, he explained, for drunken sailors, and nobody else was about.
Probably you youngsters will generally use coal-gas for filling your balloons, it being so handy. I would prefer that you did not, but use hydrogen instead, because not only is the making of hydrogen chemically instructive, but a balloon of given size will lift at least half as much again as it would if filled with gas from coal taken as one finds it. Besides, general though the use of coal-gas illumination has become, it may happen that some boy is staying at a country house where coal-gas is not available, for all which reasons I shall begin by giving directions for the production of hydrogen on a sufficiently large scale, and easily.
There are many ways of preparing hydrogen. I shall offer you the choice between two. Both are equally good, and you will discover for yourselves which is the easier under your own special circumstances. No. 1 consists in acting upon zinc or iron—zinc is best—with a mixture of one part of oil of vitriol, measure, and six parts of water, also measure. No. 2 consists in passing steam through a red-hot iron pipe, loosely packed with fragments of iron—say iron nails. If oil of vitriol be available in the out-of-the-way country house where you are assumed to operate, I recommend you to follow plan No. 1. So now about the apparatus. Two large wide-mouthed pickle or preserve bottles, with bungs to match, and a few feet of small leaden gas-pipe, are all that you will require, and you must arrange your apparatus in the following fashion. (Figs. 1 and 2.)
hydrogen productionFigs. 1 and 2.
Figs. 1 and 2.
You will here observe that one bottle is represented as larger than the other. We may call it the generator. Into it a good handful of zinc fragments having been put, or in defect of these a handful of small iron nails, and the cork thrust in tight,the mixture of oil of vitriol with water is to be poured down the upright tube ata, which you will observe has been reamed out into a sort of funnel shape by thrusting into it a conical piece of wood. It is worth while here to remark that though a large preserve bottle answers very well as a generator, yet a copper vessel answers much better, the gas development being much faster, on account of a galvanic condition, due to the contact of copper with zinc, and which on this occasion I do not consider necessary to write more about.
flower potFig. 3.
Fig. 3.
As for plan No. 2, the representation of which is annexed, it is much more simple than it looks, as you will gather when I tell you that the furnace part of the apparatus need be no more nor less than a flower-pot having the necessary holes knocked in (Fig. 3). Mind, however, to bind your flower-pot with wire, as it is sure to crack when fuel is first lighted within it. Let it crack as much as ever it pleases, your furnace will be none the worse for present purposes, and that is all you require.
I dare say you have heard of a dear departed lady, much respected in her time, a Mistress Glass. ‘First catch your hare,’ wrote Mistress Glass, when about to give directions for making hare-soup. First catch, or learn how to catch, your gas, say I. By this time you know and can judge for yourself which to use, whether hydrogen pure and simple, or else coal-gas.
Now about making your balloon. The first question is what you shall make it of. Large gas-balloons, such as ascend at public exhibitions with aëronaut travellers, are usually made of silk, covered with some sort of elastic varnish, though the material of very large balloons may be calico, linen, or even canvas. The general statement holds good that in proportion as the balloon is larger so does it admit of being made coarser and heavier. There is a sound mathematical reason for this which any sharp boy ought to perceive, and which, if he do not perceive, I would advise him for his own good to go to his mathematical master and accept castigation.
When the question was how to make a fire-balloon, solution was easy. Tissue-paper, plain and simple, leaves for this purpose nothing to be desired. If a few holes should happen to find themselves in your material, the consequence would not be very serious, inasmuch as the balloon carries its flame, its hot-air generator, along with it; but when you come to have one charge of gas, the gas not renewable, you are obliged to be particular, not merely as to holes, but even loosely packed fibres.
I am entitled to speak magisterially on this point, having recently had some professional talk over the matter with Mr. Brock, the pyrotechnist. ‘Gold-beater’s skin is the very best material for small balloons,’ was that gentleman’s remark to me,‘but it is very expensive. I want to be able to use paper, and every sort of varnish I have tried has been attended with very indifferent success.’ Mr. Brock went on to say that anybody who might succeed in rendering tissue-paper effectively gas-proof might make a fortune. Now I do not believe in the fortune-making part of the business at all, but I think I shall presently be able to tell you how to make tissue-paper effectively gas-proof. I sayeffectively, because I know that no varnished silk, cotton, or even canvas material—all used for making balloons—ever is gas-proof. If you fill the thickest ox-bladder you can get with hydrogen or coal-gas, tie the neck of it, and varnish the bladder into the bargain, still gas will come out and atmospheric air will go in. By simply looking at the closed bladder you would not fancy this had happened, because the bladder seems plump and well distended, but were you incautiously to allow a small jet of the contained gas to escape, and to ignite the jet, the whole bladder would explode with a loud report. Now neither hydrogen nor coal-gas will explode when unmixed with oxygen; it simply burns.
Having got the necessary sheets of tissue-paper, hold each of them successively between your eye and a bright light, which will disclose any absolute holes, should such exist. Having discovered them, your first care must be to stop them, and this you do by a plaster of tissue-paper smeared with solution of india-rubber in benzoline. I shall give you no proportions for this solution, but leave you to rule-o’-thumb guidance. Having charged a wide-mouthed bottle—a pickle-bottle does quite well-about half full with benzoline, put into it piece after piece of india-rubber—not vulcanised rubber, mind, which will not dissolve in benzoline, but raw rubber, and keep adding rubber, bit by bit, stirring occasionally with a table knife until you get a paste, not too thick for spreading with a knife-blade. The solution will not be complete for some days. With this, when complete, smear a breadth of tissue-paper, and consider it your plaster.
Remember well the following injunction. In any case when you desire to stick together two surfaces with this india-rubber cement, both surfaces must be smeared, as it does not suffice to smear only one. The next injunction is a very peculiar one, and would not be likely to come self-suggested. Do not bring the surfaces together whilst the solution is wet. Let your work stand until evaporation of the solvent benzoline has left the surfaces what may be called dry. Thus you see the working with this india-rubber paste is the very reverse of working with all ordinary sticking materials.
Repeat the plastering on of solution at least twice, and plaster thick; the result is thin enough when dry. Having in this manner stopped the holes, proceed to make the paper gas-proof. For this purpose you will need a special solution, made in this wise:—To a pint of benzoline add an ounce of solid paraffin—some of a paraffin candle, for example—and a drachm of raw, not vulcanised, rubber. When the two have dissolved, which will require some days’ waiting, lay your tissue-paper on a table, and by means of a flat varnish-brush spread the solution all over it. Wait till evaporation leaves the paper dry, then repeat the operation up to six times, when the paper will have been rendered sufficiently gas-proof for making a balloon. You are to cut this out into fillets, just as you did when making a fire-balloon, and you are to stick the fillets together with the cement already described, remembering well the two injunctions already given. You arenot restricted to shape as you are in fire-balloon making, but may adopt any shape, remembering, however, that to promote convenience of gas-collection, the balloon neck should be much narrower than that of a fire-balloon; tubular, so to speak, a tube of one inch diameter being quite sufficient. The reason for making a narrow tubular neck will be apparent from study of the accompanyingdiagram. It will be evident to you that on account of the narrow neck the mode of car, or weight attachment, cannot be similar to that adopted in the case of fire-balloons. The neatest and, at the same time, most obvious plan of procedure is that adopted in large balloons, by throwing a net, with strings dependent, over the whole balloon, and attaching the car or other weights to the pendent strings. Such elaborate work is, however, quite unnecessary in toy balloons. A length of cord tied round the neck and allowed to hang down affords every necessary facility for further attachment.